Also in 1868, he married Esther A. Benoist,[3] a daughter of pioneer St. Louis banker Louis Auguste Benoist. They had four children: Louis, Condé, Ethel, and Estelle.

While living in Europe, William Nast filed for several invention patents, including one for "improvements in the treatment of stable manure, and in the manufacture of paper" on July 6, 1876, awarded February 22, 1878,[4] and one for "improvements in the manufacture of dextrine, sugar and the like, from cellulose and ligneous materials" on November 4, 1880,[5] and US 374618 "Obtaining ammonia from manure", awarded on December 13, 1887.[6]